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Continuing existing time-dependent solutions

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Hi, if I have an existing time-dependent solution that was successfully executed from 0 to 1 sec (say). Say later I want to run it from 1 sec to 2, what would be the best way to do this? 1. Do I have to ad a new time-dependent study and somehow point to this solution? 2. How does this change if say I want run the new simulation from 0.8 sec to 2?

On other platforms, there are "restart" files that are written out, the timing and frequency of which is user controlled that allows you to simply point to the time instant from where a restart is needed. Is there something similar in COMSOL? Thanks !


3 Replies Last Post Jun 28, 2021, 4:01 a.m. EDT
Edgar J. Kaiser Certified Consultant

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Posted: 11 months ago Jun 25, 2021, 7:58 a.m. EDT

Hi,

it is interesting that you can continue a time dependent solution if you stop the solver before it completes using the stop buttons in the progress tab. In this case the study shows a 'Continue' button. You may then increase the setting for the run time of the study before you continue. Don't use the hard stop, the red bullet with the cross for that. You will lose the solution with that. After the solver completes the preset runtime, the 'Continue' option is no longer available, for what reason ever. I requested to keep it available a few times. Sometimes I stop a solution before it completes if I am not sure if my time range is sufficient, to keep the continue option alive.

If you want to continue an existing completed time dependent study you can set up a new study and point to the last (or any) timestep for the initial values in the study step settings. You can also merge the two solutions to have a comprehensive solution for the post processing.

All in all it would be convenient to simply allow continuation also after a completed time dependent study.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi, it is interesting that you can continue a time dependent solution if you stop the solver before it completes using the stop buttons in the progress tab. In this case the study shows a 'Continue' button. You may then increase the setting for the run time of the study before you continue. Don't use the hard stop, the red bullet with the cross for that. You will lose the solution with that. After the solver completes the preset runtime, the 'Continue' option is no longer available, for what reason ever. I requested to keep it available a few times. Sometimes I stop a solution before it completes if I am not sure if my time range is sufficient, to keep the continue option alive. If you want to continue an existing completed time dependent study you can set up a new study and point to the last (or any) timestep for the initial values in the study step settings. You can also merge the two solutions to have a comprehensive solution for the post processing. All in all it would be convenient to simply allow continuation also after a completed time dependent study. Cheers Edgar

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Posted: 11 months ago Jun 27, 2021, 2:28 p.m. EDT

I see, this is helpful, but definitely frustrating and coming from a background in open source code writing, have "restart" files was the first thing we did. Essentially at periodic user-specified intervals, we would store a bunch of data including variables, mesh etc. in a file which could be re-read in case of a crash or if the user was to change things but not start the simulation from beginning.

But do appreciate your suggestion, will use that till a more convenient option becomes accessible.

Thanks Advitya

I see, this is helpful, but definitely frustrating and coming from a background in open source code writing, have "restart" files was the first thing we did. Essentially at periodic user-specified intervals, we would store a bunch of data including variables, mesh etc. in a file which could be re-read in case of a crash or if the user was to change things but not start the simulation from beginning. But do appreciate your suggestion, will use that till a more convenient option becomes accessible. Thanks Advitya

Edgar J. Kaiser Certified Consultant

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Posted: 11 months ago Jun 28, 2021, 4:01 a.m. EDT

Hi Advitya,

you can activate the 'recovery file' in the preferences to account for a crash. With the recovery file you can in many cases continue a crashed solution. It isn't working always, it depends a bit which way the crash occurred, but I have it on always.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Advitya, you can activate the 'recovery file' in the preferences to account for a crash. With the recovery file you can in many cases continue a crashed solution. It isn't working always, it depends a bit which way the crash occurred, but I have it on always. Cheers Edgar

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